Cap assembly for a second battery and second battery

ABSTRACT

The present disclosure provides a cap assembly for a secondary battery and a secondary battery. The cap assembly includes a cap plate, a fixing member, a connecting member and an electrode terminal, wherein the cap plate has an electrode lead-out hole; the fixing member is fixed to the cap plate through the connecting member and provided with a weakened portion that is close to a center line of the cap plate in a width direction of the cap plate; and the electrode terminal includes a terminal board, wherein the terminal board has an outer peripheral surface at least partially surrounded by the fixing member so that the electrode terminal is fixed to the fixing member, and the terminal board is provided on a side of the cap plate and covers the electrode lead-out hole.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims priority to Chinese PatentApplication No. 201710935598.7, filed on Oct. 10, 2017, the content ofwhich is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to the technical field of energy storagedevices, and in particular, to a cap assembly for a secondary batteryand a secondary battery.

BACKGROUND

New energy vehicles are widely promoted in the country and even in theworld. However, in order to completely replace fuel vehicles, there aremany areas for improvement. For example, there are a few problems suchas low travelling mileages of vehicles, high cost of battery packs,reliability of battery packs and the like, which need to be furthersolved.

Currently, a power battery usually adopts a square hard shell structure.A shell of the power battery includes a case and a cap assembly. Theshell of the power battery provides a closed space for accommodating anelectrode assembly and electrolyte. The power of the electrode assemblyis led out of the closed space through a terminal of the cap assembly.

In a conventional cap assembly, a manner of fixing the terminal is asfollows: a cap plate is provided with a through hole; the terminalincludes a base portion and an extension portion; and the base portionhas a cross-sectional area larger than an area of the through hole.During assembly, the base portion is located under the cap plate (i.e.inside the case), and the extension portion is fixed by a clamp springor a riveting member after passing through the through hole. In thisway, the terminal is fixed to the cap plate. With such a fixing manner,the cap assembly may employ a large number of mechanical components,thereby increasing the cost of the secondary battery and reducing thereliability of the cap assembly. Meanwhile, since the base portion islocated inside the case, space utilization inside the case may bereduced and thus energy density of the power battery may be reduced. Inorder to solve this problem, a terminal board may be employed to bedisposed at a side of the cap plate; a fixing member and a connectingmember may be provided; the fixing member may be fixed to the cap platethrough the connecting member; and at least part of an outer peripheralsurface of the terminal board may be surrounded by the fixing member sothat the terminal board may be fixed to the fixing member. However, whenthe cap plate is deformed to form an arch due to a large amount of gasgenerated inside the case of the secondary battery (the cap plate isdeformed to form an arch because two edges of the cap plate in its widthdirection are welded to the case, the deformations of the two edges inthe width direction are small, and the deformation of a middle region ofthe cap plate in the width direction is large), due to a large rigidityof the fixing member, the fixing member may not form an arch along withthe cap plate, so the gaps between two sides of the cap plate in thewidth direction and the fixing member may be increased (even theconnecting member may be pulled off). Thus it may not be possible totightly press a sealing member between the terminal board and the capplate, thereby causing air leakage or liquid leakage of the secondarybattery.

SUMMARY

According to an aspect of the present disclosure, a cap assembly for asecondary battery is provided. The cap assembly includes a cap plate, afixing member, a connecting member and an electrode terminal, whereinthe cap plate has an electrode lead-out hole; the fixing member is fixedto the cap plate through the connecting member and provided with aweakened portion that is close to a center line of the cap plate in awidth direction of the cap plate; and the electrode terminal includes aterminal board, wherein the terminal board has an outer peripheralsurface at least partially surrounded by the fixing member so that theelectrode terminal is fixed to the fixing member, and the terminal boardis provided on a side of the cap plate and covers the electrode lead-outhole.

According to an aspect of the present disclosure, the fixing memberincludes at least two weakened portions that are respectively located ontwo sides of the electrode lead-out hole in a length direction of thecap plate as well as on the center line of the cap plate in the widthdirection of the cap plate.

According to an aspect of the present disclosure, the weakened portionincludes an opening portion that is formed on a surface of the fixingmember on a side away from the cap plate.

According to an aspect of the present disclosure, the opening portionpenetrates through the fixing member along a length direction of the capplate; or the opening portion penetrates through the fixing member alonga thickness direction of the cap plate.

According to an aspect of the present disclosure, one of the terminalboard and the fixing member is provided with a recess, and the other oneof the terminal board and the fixing member is provided with aprotrusion to be matched with the recess, so that relative rotationbetween the electrode terminal and the fixing member is limited byengagement of the recess and the protrusion.

According to an aspect of the present disclosure, the recess is providedon the outer peripheral surface of the terminal board, and theprotrusion to be matched with the recess is provided on an inner surfaceof the fixing member in contact with the terminal board.

According to an aspect of the present disclosure, the terminal board isprovided with a notch on a surface of the terminal board on a side closeto the cap plate or on a side away from the cap plate, and the notchextends along a length direction of the cap plate and is close to thecenter line of the cap plate in the width direction of the cap plate.

According to an aspect of the present disclosure, the connecting memberincludes an undercut and an undercut hole; the undercut hole is providedon a surface of the cap plate facing the fixing member; the undercuthole has an aperture gradually increasing along a direction from thefixing member to the cap plate; and the undercut is connected to thefixing member and has a shape adapted to a shape of the undercut hole soas to be engaged with the undercut hole.

According to an aspect of the present disclosure, the cap assemblyfurther includes a sealing member that is provided between the terminalboard and the cap plate and surrounds the electrode lead-out hole so asto seal the electrode lead-out hole.

According to an aspect of the present disclosure, the sealing member isprovided with an annular groove on a surface of the sealing member on aside facing the cap plate; the cap plate is provided with an annularflange to be matched with the groove on a surface of the cap plate on aside facing the sealing member; and the flange is inserted into thegroove.

According to another aspect of the present disclosure, a secondarybattery is provided. The secondary battery includes a case having anopening; an electrode assembly accommodated in the case, including afirst electrode plate, a second electrode plate and a separator disposedbetween the first electrode plate and the second electrode plate; andthe cap assembly as described above, wherein the cap assembly covers theopening of the case so as to enclose the electrode assembly in the case.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood from the followingdescriptions of specific embodiments of the present disclosure by takenin conjunction with the accompanying drawings, in which:

Other features, objects, and advantages of the present disclosure willbecome more apparent by reading the following detailed descriptions ofnon-limiting embodiments with reference to the accompanying drawings, inwhich the same or similar reference signs denote the same or similarfeatures.

FIG. 1 is a schematic diagram of an exploded structure of a cap assemblyaccording to an embodiment of the present disclosure;

FIG. 2 is a schematic top view of a structure of the cap assembly ofFIG. 1;

FIG. 3 is a schematic diagram of a cross-sectional structure of the capassembly of FIG. 2 taken along a section line A-A;

FIG. 4 is a schematic diagram of a cross-sectional structure of a capplate in the cap assembly of FIGS. 1 to 3 taken along a lengthdirection;

FIG. 5 is an enlarged partial view of a portion A of the cap assembly ofFIG. 3;

FIG. 6 is a schematic diagram of a three-dimensional structure of acertain state of a fixing member according to a first embodiment;

FIG. 7 is a schematic diagram of a three-dimensional structure of aterminal board according to a first embodiment of the presentdisclosure;

FIG. 8 is a schematic diagram of a three-dimensional structure of aterminal board according to a second embodiment of the presentdisclosure;

FIG. 9 is a schematic diagram of a three-dimensional structure ofanother state of the fixing member of FIG. 6;

FIG. 10 is a schematic diagram of a three-dimensional structure of afixing member according to a second embodiment of the presentdisclosure; and

FIG. 11 is a schematic diagram of a three-dimensional structure of aterminal board according to a third embodiment of the presentdisclosure.

REFERENCE LABELS IN THE FIGURES

-   100—Cap assembly-   10—Cap plate-   11—Electrode lead-out hole-   12—Depressed portion-   13—Undercut hole-   14—Liquid injection hole-   15—Anti-explosion valve assembly-   16—Flange-   20—Terminal assembly-   21—Terminal board-   211—Depressed portion-   212—Recess-   213—Recess-   214—Notch-   22—Fixing member-   221—Through hole-   222—Accommodation space-   223—Protrusion-   224—Opening portion-   225—Undercut-   226—Opening portion-   23—Sealing member-   231—Groove-   30—Terminal assembly-   32—Fixing member-   33—Sealing member-   40—Lower insulator-   41—Undercut

DETAILED DESCRIPTION

The features and exemplary embodiments of the various aspects of thepresent disclosure will be described in detail below. In the followingdetailed description, numerous specific details are set forth in orderto provide a thorough understanding of the present disclosure. It willbe apparent, however, to those skilled in the art that the presentdisclosure may be practiced without some of these specific details. Thefollowing description of embodiments is only provided by illustratingexamples for a better understanding of the present disclosure. In thedrawings and the following description, at least a part of well-knownstructures and techniques are not shown in order to avoid unnecessarilyobscuring the present disclosure. Further, for clarity, the size of apart of the structures may be exaggerated. The same reference numeralsin the drawings denote the same or similar structures, and thus theirdetailed description will be omitted. Furthermore, the features,structures, or characteristics described below can be combined in anysuitable manner in one or more embodiments.

The terms denoting directions that appear in the following descriptionindicate directions shown in the drawings, and do not limit specificstructures of the cap assembly and the secondary battery of the presentdisclosure. In the description of the present disclosure, it should alsobe noted that the terms “mounted”, “connected” and “connection” shouldbe interpreted in a broad sense unless explicitly defined and limitedotherwise. For example, it may indicate “fixed connection”, “disassembleconnection” or “integral connection”; it may indicate a directconnection or an indirect connection. For those skilled in the art,specific meanings of the above terms in the present disclosure may beunderstood depending on specific situations.

The cap assembly of the secondary battery provided by an embodiment ofthe present disclosure can be connected at an opening of a case of thesecondary battery to seal an electrode assembly and electrolyte into thecase and enable an electrical connection between the electrode assemblyand conductive parts outside the case. The cap assembly according to theembodiment of the present disclosure can reduce the occupancy of aninternal space of the battery case while ensuring the sealing effect ofthe battery case. Therefore, energy density of the secondary battery canbe increased, and reliability of the secondary battery in use can beensured.

For a better understanding of the present disclosure, a cap assembly ofa secondary battery and the secondary battery according to embodimentsof the present disclosure will be described in detail below withreference to FIG. 1 to FIG. 11.

FIG. 1 is a schematic diagram of an exploded structure of a cap assembly100 according to an embodiment of the present disclosure; FIG. 2 is aschematic top view of a structure of the cap assembly 100 of FIG. 1;FIG. 3 is a cross-sectional structural diagram of the cap assembly 100of FIG. 2 taken along a section line A-A. The structure diagram of thesecondary battery is not shown in the figures. The secondary battery maygenerally include a cap assembly 100, a case and an electrode assemblylocated inside the case.

According to an embodiment of the present disclosure, the case may bemade of metal material, such as aluminum, aluminum alloy, ornickel-plated steel. The case is formed in a rectangular box shape andhas an opening to communicate to its inside accommodation space.

The electrode assembly may be formed by stacking or winding a firstelectrode plate, a second electrode plate, and a separator together,where the separator is an insulator interposed between the firstelectrode plate and the second electrode plate. In this embodiment, asan example, the description will be provided by taking the firstelectrode plate as a positive electrode plate and the second electrodeplate as a negative electrode plate. Similarly, in other embodiments,the first electrode plate may be a negative electrode plate, and thesecond electrode plate may be a positive electrode plate. In addition,active materials for the positive electrode plate may be coated on acoating area of the positive electrode plate, and active materials forthe negative electrode plate may be coated on a coating area of thenegative electrode plate. A portion extending from the coating area ofthe first electrode plate is referred to as an electrode tab, i.e., afirst electrode tab; and a portion extending from the coating area ofthe second electrode plate is referred to as a negative electrode tab,i.e., a second electrode tab (not shown in the figures).

The cap assembly 100 may be used to seal the case. The electrodeassembly may be sealed in the case by the cap assembly 100 that isconnected at the opening of the case. According to an embodiment of thepresent disclosure, the cap assembly 100 may generally include a capplate 10, a terminal assembly 20, a terminal assembly 30 and a lowerinsulator 40.

FIG. 4 is a schematic diagram of a cross-sectional structure of a capplate in the cap assembly of FIGS. 1 to 3 taken along a lengthdirection. As shown in FIG. 4, the cap plate 10 may be in the shape of athin plate and have a size and shape matched with the opening of thecase 200 so as to be capable of being connected at the opening of thecase. The cap plate 10 may be made of metal material, for example, thesame metal material as that of the case. In the embodiment, the capplate 10 is provided with an electrode lead-out hole 11, a depressedportion 12, an undercut hole 13, a liquid injection hole 14 and ananti-explosion valve assembly 15.

The liquid injection hole 14 is formed on the cap plate 10 in apredetermined size, so that the electrolyte can be injected into thecase through the liquid injection hole 14 after the cap plate 10 coversthe opening of the case and is hermetically connected with the case. Theanti-explosion valve assembly 15 may have a conventional structure (forexample, by providing a rupture disk) and may be disposed at asubstantially central position of the cap plate 10. When the gaspressure inside the second battery becomes too large as a result ofover-charging, over-discharging, or over-heating of the second battery,the rupture disk in the anti-explosion valve assembly 15 can be brokenso that the gas produced inside the secondary battery can be exhaustedto the outside via a through hole of the anti-explosion valve assembly15, thereby being able to prevent the secondary battery from exploding.

FIG. 5 is an enlarged partial view of a portion A of the cap assembly100 of FIG. 3; FIG. 6 is a schematic diagram of a three-dimensionalstructure of a certain state of a fixing member 22 according to a firstembodiment; FIG. 7 is a schematic diagram of a three-dimensionalstructure of a terminal board 21 according to a first embodiment of thepresent disclosure. With reference to FIG. 1 and FIGS. 5 to 7, accordingto an exemplary embodiment, the cap plate 10 may be provided with twoelectrode lead-out holes 11 for leading electric energy in the electrodeassembly inside the case out of the cap plate 10. In an exemplaryembodiment, the terminal assembly 20 may generally include a firstelectrode terminal, a fixing member 22 and a sealing member 23;likewise, the terminal assembly 30 may generally include a secondelectrode terminal, a fixing member 32 and a sealing member 33. Thefollowing description is merely given by way of example with thestructure of the terminal assembly 20 and its mounting form on the capplate 10. Also by way of example, the following description is given byassuming the terminal assembly 20 is a positive electrode terminalassembly and the terminal assembly 30 is a negative electrode terminalassembly.

The first electrode terminal may include a terminal board 21. In theembodiment, for example, the terminal board 21 has a structure of acircular (and alternatively square) sheet or plate, and an outerperipheral surface of the terminal board 21 is at least partiallysurrounded by the fixing member 22. In this way, the terminal board 21may be mounted to the fixing member 22 and thus fixed to the cap plate10 through the fixing member 22. In an alternative embodiment, the firstelectrode terminal may be a plate-like structure, and a surface of thefirst electrode terminal close to the cap plate 10 does not exceed asurface of the cap plate 10 close to the first electrode terminal (i.e.,the first electrode terminal is composed of the terminal board 21 anddoes not protrude into the electrode lead-out hole 11).

The fixing member 22 may be a plastic member and integrally molded tothe outer periphery of the terminal board 21. In an exemplaryembodiment, the fixing member 22 is a hard plastic member. For example,the fixing member 22 may be made of high-temperature-resistantinsulating plastic material such as one or more of polyphenylene sulfide(PPS), perfluoroalkoxy resin (PFA) or polypropylene (PP) by an integralinjection molding process.

The fixing member 22 as shown in FIG. 6 is the fixing member 22 in thecap assembly 100 of FIGS. 1 to 3. In the embodiment, as an example, thefixing member 22 has a rotary structure and has an accommodation space222 adapted to the shape of the terminal board 21. The accommodationspace 222 is an annular receiving groove formed on an inner wall surfaceof a through hole 221 in a circumferential direction, so that theterminal board 21 may be accommodated in the accommodation space 222 andfixed to the terminal board 21. In this case, a part of the fixing part22 may be clamped between the terminal board 21 and the cap plate 10.

In an alternative embodiment, in order to increase the fastening forcewith which the terminal board 21 and the fixing member 22 are engagedwith each other, one of the terminal board 21 and the fixing member 22may be provided with a recess and the other one of the terminal board 21and the fixing member 22 may be provided with a protrusion adapted tothe recess. Thus the electrode terminal and the fixing member 22 arerestrained from rotating relative to each other by the fitted engagementof the recess and the protrusion. In the embodiment, the terminal board21 is provided with a recess 212, and the fixing member 22 is providedwith a protrusion 223 corresponding to the recess 212 of the terminalboard 21.

With reference to both FIG. 6 and FIG. 7, exemplarily, the outerperipheral surface of the terminal board 21 is provided with a pluralityof recesses 212 which are radially opened notches along the outerperipheral surface of the terminal plate 21, and each of the recesses212 penetrates through the terminal board 21 in the thickness directionof the terminal board 21. The plurality of recesses 212 are spaced apartand evenly arranged in the circumferential direction of the terminalboard 21. Correspondingly, protrusions 223 matched with the recesses 212of the terminal board 21 are provided on an inner wall surface of thefixing member 22 in contact with the terminal board 21, that is, in theaccommodation space 222. Again, the protrusions 223 of the fixing member22 are radially protruded from the inner wall surface of theaccommodation space 222. As such, when the terminal board 21 is placedin the accommodation space 222 of the fixing member 22, the recesses 212and the protrusions 223 are engaged with each other in a snap-fit mannerso that the terminal board 21 can be firmly connected with the fixingmember 22. Therefore, it is possible to prevent the terminal board 21and the fixing member 22 from rotating relative to each other to affectthe structural stability of the cap assembly 100. At the same time, byproviding the recesses 212 and the protrusions 223 that are fitted witheach other, the contact area between the terminal board 21 and thefixing member 22 can be increased, and thus the engaging force betweenthe terminal board 21 and the fixing member 22 can be further increased.

Since the terminal board 21 and the fixing member 22 in the embodimentof the present disclosure are formed by integrally injection molding,the specific shape of the recess 212 provided on the terminal board 21may not be limited, and the recess 212 may be a regular or irregularnotch. In addition, in the embodiment of the present disclosure, thedepth of the recess 212 in the radial direction of the terminal board 21is not limited, as long as the recess 212 can be fitted with theprotrusion provided on the fixing member 22 and the provision of therecess 212 may not affect the performance of basic functions of theterminal board 21.

Of course, as shown in FIG. 7, the terminal board 21 may be providedwith four recesses 212 in the circumferential direction, and two of therecesses 212 may be opposite to the other two of the recesses 212respectively. Alternatively, only two recesses 212 opposite to eachother may be provided, or more recesses 212 may be provided along thecircumferential direction of the terminal board 21.

In addition, in order to fit with the accommodation space 222, anannular depressed portion 211 may be provided on the surface of the sideof the terminal board 21 far away from the cap plate 10 in thecircumferential direction. As such, the fixing member 22 can wrap thesurface of the terminal board 21 on the side far away from the cap plate10, so that the fixing member 22 can be more firmly engaged with theterminal board 21. Meanwhile, after the terminal board 21 and the fixingmember 22 are engaged with each other and mounted on the cap plate 10,the overall thickness of the cap assembly 100 will not be increased, sothat the space occupied by the secondary battery in the height directioncan be saved to improve the energy density of the secondary battery.After the first electrode terminal and the fixing member 22 areconnected to each other, the terminal board 21 covers the electrodelead-out hole 11 and the outer peripheral surface of the terminal board21 protrudes from the inner wall of the electrode lead-out hole 11(i.e., as shown in FIG. 4, the cross-sectional size of the terminalboard 21 is greater than the cross-sectional size of the electrodelead-out hole 11), and the surface of the terminal board 21 far awayfrom the cap plate 10 protrudes from the surface of the fixing member 22far away from the cap plate 10 (i.e., the top surface of the terminalboard 21 is higher than the top surface of the fixing member 22). Also,the through hole 221 is provided on the side of the fixing member 22close to the cap plate 10 so that the terminal board 21 can be exposedinside the case via the through hole to be electrically connected withthe electrode assembly.

Of course, the embodiment of the present disclosure is not limitedthereto. In other embodiments, a protrusion may be provided on the outercircumferential surface of the terminal board 21, and correspondingly, arecess to be engaged with the protrusion may be provided on the innerwall surface of the fixing member 22 in contact with the terminal board21. Likewise, it is also possible to achieve the purpose of restrictingthe relative rotation between the terminal board 21 and the fixingmember 22. In addition, the dimensions of the recess and the protrusionin the thickness directions of the terminal plate 21 and the fixingmember 22 are not limited in the embodiment of the present disclosure.In the above embodiment, the recesses are all provided to penetratethrough the thickness of the terminal board 21. However, in otherembodiments, the recess may be provided not to penetrate through thethickness of the terminal board 21, but may also be engaged with thecorresponding protrusion of the fixing member 22 to prevent relativerotation between the terminal board 21 and the fixing member 22.

FIG. 8 is a schematic diagram of a three-dimensional structure of aterminal board 21 according to a second embodiment of the presentdisclosure. In the embodiment, the same parts in the terminal board 21as in the terminal board 21 of the first embodiment are denoted by thesame reference numerals, and the already described parts will not bedescribed again. As shown in FIG. 8, different from the terminal board21 of the first embodiment, in the present embodiment, in order toprevent relative rotation between the terminal board 21 and the fixingmember 22, a recess 213 is provided on the terminal board 21, and therecess 213 is a through hole penetrating through the terminal board 21in the thickness direction thereof. Correspondingly, a post (i.e., aprotrusion, not shown in the figure) to be matched with the recess 213is protruded from the surface of the fixing member 22 in contact withthe terminal board 21. Since the peripheral edge of the terminal board21 is embedded in the accommodation space 222 of the fixing member 22,the fixing member 22 can be provided with the above-mentioned post on anupper surface and/or a lower surface of the accommodation space 222 tobe matched with the recess 213 of the terminal board 21.

Therefore, when the terminal board 21 is received in the accommodationspace 222, the post provided in the fixing member 22 may be insertedinto the recess 213 of the terminal board 21, so that the terminal board21 can be firmly connected to the fixing member 22 by the snap fit ofthe recess 213 and the post. Of course, in other embodiments, the recess213 may also be disposed to not penetrate through the terminal board 21but only penetrate a predetermined depth in the thickness direction ofthe terminal board 21 to be engaged with the corresponding post providedin the fixing member 22. Again, it is also possible to achieve thepurpose of restricting the relative movement between the terminal board21 and the fixing member 22.

FIG. 9 is a schematic diagram of a three-dimensional structure ofanother state of the fixing member 22 of FIG. 6. As shown in FIG. 1,FIG. 5 and FIG. 9, in order to fix the fixing member 22 to the cap plate10, a connecting member including an undercut 225 and an undercut hole13 may be further provided. The undercut 225 and the undercut hole 13are correspondingly provided between the fixing member 22 and the capplate 10 so as to be engaged with each other.

Particularly, at a surface of the cap plate 10 facing the terminal board21, a plurality of undercut holes 13 may be disposed around theelectrode lead-out hole 11. The plurality of undercut holes 13 may bearranged with regular intervals along the circumference, and an apertureof each undercut hole 13 may gradually increase along the direction fromthe fixing member 22 to the cap plate 10. Of course, the increasing ofthe aperture as mentioned herein does not require that the aperture ofthe undercut hole 13 regularly increases along the direction from thefixing member 22 to the cap plate 10, but means that the aperture of oneend of the undercut hole 13 far away from the fixing member 22 is largerthan that of the other end of the undercut hole 13 close to the fixingmember 22. In other words, it is only required that the aperture of thebottom of the undercut hole 13 is larger than the aperture of the top ofthe undercut hole 13 so as to allow for the engagement between theundercut 225 and the undercut hole 13. Correspondingly, the undercut 225adapted to the shape of the undercut hole 13 is provided at a surface ofthe fixing member 22 facing the cap plate 10. Thus, the fixing member 22can be firmly fixed to the cap plate 10 by the engagement between theundercut 225 provided on the fixing member 22 and the undercut hole 13provided on the cap plate 10. In this way, the fixing member 22 can betightly fixed to the cap plate 10 by a simple structure to simplify thestructure of the cap assembly 100, and meanwhile, the productivity andstructural stability of the cap assembly 100 can be improved.

As shown in FIGS. 1 and 5, the sealing member 23 is provided between theterminal board 21 and the cap plate 10 and surrounds the electrodelead-out hole 11. In this embodiment, specifically, the sealing member23 may be of an annular shape and provided with an annular groove 231 onthe surface thereof facing the cap plate 10. The cap plate 10 may beprovided with an annular flange 16 surrounding the electrode lead-outhole 11 on the side of the cap plate 10 facing the sealing member 23, sothat the flange 16 of the cap plate 10 can be engaged with the groove231. The terminal board 21 can press the sealing member 23 tightlytoward the cap plate 10 under the fastening force of the fixing member22, so that the sealing member 23 between the flange 16 and the terminalboard 21 can be pressed tightly to make the sealing member 23 be inclose contact with the terminal board 21 through the flange 16 and forma sealing line between the terminal board 21 and the cap plate 10. Thus,it is possible to improve the sealing between the terminal board 21 andthe cap plate 10 and avoid the problem of liquid leakage due to badsealing between the terminal board 21 and the cap plate 10, therebyfurther improve the reliability of use of the secondary battery.

In this embodiment, since the terminal board 21 is mounted on the capplate 10 from top to bottom, the terminal board 21 may always apply apressing force to the sealing member 23 under the effect of thefastening force of the fixing member 22 and the gravity of the terminalboard 21 and the fixing member 22. Accordingly, the sealing performanceof the sealing member 23 can be further improved. Also, the provision ofthe sealing member 23 outside the case can reduce the probability thatthe sealing member 23 may contact with the electrolyte inside the case.

During use of the secondary battery, when the pressure inside the caseincreases, the cap plate 10 may arch substantially along a center linein its width direction. When the cap plate 10 is deformed, the fixingmember 22 generally does not deform due to the rigidity of the fixingmember 22. In this case, it is possible to cause increased gaps betweenthe fixing member 22 and both sides of the cap plate 10 in the widthdirection, so that the sealing member 23 cannot be pressed tightlybetween the terminal board 21 and the cap plate 10. For example, theundercuts 225 close to both sides of the cap plate 10 in the widthdirection of FIG. 5 may be disengaged from the undercut holes 13, sothat the sealing member 23 cannot be pressed tightly by the terminalboard 21 and the cap plate 10. In order to avoid an increase of gapsbetween the fixing member 22 and both sides of the cap plate 10 in thewidth direction and make the sealing member 23 be always pressed tightlybetween the terminal board 21 and the cap plate 10, the fixing member 22may be further provided with a weakened portion so as to allow thefixing member 22 to deform along with the cap plate 10.

With continued reference to FIG. 1 and FIG. 6, in an alternativeembodiment, the weakened portion of the fixing member 22 is close to thecenter line of the cap plate 10 in the width direction thereof. In thisembodiment, since the fixing member 22 is a rotating body and the fixingmember 22 includes two weakened portions, the two weakened portions aredisposed on two opposite sides of the fixing member 22 in the radialdirection. That is, the two weakened portions are respectively locatedon two sides of the electrode lead-out hole 11 in the length directionof the cap plate 10 (i.e., two sides of the through hole 221 in thelength direction of the cap plate 10) and close to the center line ofthe cap plate 10 in the width direction thereof. The weakened portion ofthe fixing member 22 is close to the center line of the cap plate 10 inthe width direction thereof means that the position of the weakenedportion of the fixing member 22 needs to be distributed along the centerline of the cap plate 10 in the width direction thereof so that thefixing member 22 can arch along the center line of the cap plate 10 inthe width direction thereof and deform together with the cap plate 10.However, a certain error is allowed between the position of the weakenedportion and the center line of the cap plate 10 in the width directionthereof, as long as the error does not affect the deformation of thefixing member together with the cap plate 10 so that the undercut 225and the undercut hole 13 can keep in the status of being engaged witheach other.

As an example, the weakened portion may be formed on the fixing member22 by the provision of an opening portion 224. As shown in FIG. 6, theopening portion 224 may be formed on the side of the fixing member 22facing away from the cap plate 10 along the thickness direction of thefixing member 22. The opening portion 224 is formed to have apredetermined depth in the thickness direction of the fixing member 22.The opening portion 224 is respectively opened on two sides of thefixing member 22 in the radial direction of the fixing member 22, so asto form notches that are provided on opposite sides of the through hole221 of the fixing member 22 and connected to each other through thethrough hole 221 (i.e., the opening portion 224 penetrates through thefixing member 22 along the length direction of the cap plate 10).Therefore, by providing the opening portion 224 on opposite sides of thethrough hole 221 to form the weakened portion, the connection area ofthe fixing member 22 can be effectively reduced so that the fixingmember 22 can be easily deformed along the weakened portion.

Thus, by providing the weakened portion on two sides of the through hole221 of the fixing member 22 along the center line of the cap plate 10 inthe width direction thereof, the fixing member 22 can be more easilydeformed along the weakened portion. When the cap plate 10 is deformedand arched by a thrust force of the gas generated inside the case, thefixing member 22 can be arched along the weakened portion at the centerline of the cap plate 10 in the width direction thereof together withthe cap plate 10, so as to ensure that the undercut 225 and the undercuthole 13 are always in the snap fit state. Therefore, it is possible toprevent the fixing member 22 from being detached from the cap plate 10,improve the reliability of the use of the secondary battery and increasethe service life of the secondary battery. At the same time, since it isnot necessary to increase the strength of the cap plate 10 by increasingthe thickness of the cap plate 10, the manufacturing cost of the capassembly 100 can also be saved.

Of course, there is no limitation on the number of weakened portions onthe fixing member 22. In other embodiments, more weakened portions maybe provided on the fixing member 22, and preferably arranged on twosides of the through hole 221 along the length direction of cap plate10. As a result, the fixing member 22 can be more easily deformed alongwith the cap plate 10 when the cap plate 10 is arched due to the gasinside the case. Also, the fixing member 22 can be more fitted with thearc formed by the cap plate 10 when the fixing member 22 is deformedalong with the cap plate 10, so as to further ensure the stability ofthe connection between the undercut 225 and the undercut hole 13. Itshould be noted that it is necessary to provide the weakened portion onthe fixing member 22 without affecting the structural stability of thefixing member 22 itself and ensure that the terminal plate 21 can befixed to the cap plate 10 by the fixing member 22.

FIG. 10 is a schematic diagram of a three-dimensional structure of afixing member 22 according to a second embodiment of the presentdisclosure. For ease of understanding, the same structures as in thefixing member 22 of the above embodiment are denoted by the samereference numerals, and the already described structures will not bedescribed again. In the second embodiment, a weakened portion may beformed by the provision of an opening portion 226. Likewise, the openingportion 226 may also be provided on two sides of the through hole 221along the length direction of the cap plate 10 and close to the centerline of the cap plate 10 in the width direction thereof, and preferablybe located along the center line of the cap plate 10 in the widthdirection thereof. However, the difference from the opening portion 224in the above embodiment is that the opening portion 226 is a holedisposed on the surface of the fixing member 22 far away from the capplate 10 and the opening portion 226 penetrates through the fixingmember 22 in the thickness direction of the fixing member 22 (i.e.,penetrates through the fixing member 22 in the thickness direction ofthe cap plate 10).

Thus, by providing the opening portion 226 on two sides of the throughhole 221 to form the weakened portion, the connection area of the fixingmember 22 can be effectively reduced so that the fixing member 22 can beeasily deformed along the weakened portion. When the cap plate 10 isdeformed and arched by a thrust force of the gas generated inside thecase, the fixing member 22 can be arched along the weakened portion atthe center line of the cap plate 10 in the width direction thereoftogether with the cap plate 10, so as to ensure that the undercut 225and the undercut hole 13 are always in the snap fit state.

Based on the above embodiments, a recess 212 and a protrusion 223capable of fitting with the recess 212 are correspondingly disposedbetween the terminal board 21 and the fixing member 22. In analternative embodiment, the recess 212 provided along the outerperipheral surface of the terminal board 21 is located on the centerline of the cap plate 10 in the width direction thereof. That is, theouter periphery of the terminal board 21 has at least two recesses 212opposed to each other in the radial direction, and the two recesses 212are located on the center line of the cap plate 10 in the widthdirection thereof. Therefore, by providing openings at both ends of thecenter line of the terminal board 21 in the width direction of the capplate 10, a weakened area is formed at a portion of the terminal board21 between the openings at both ends. In this way, the terminal board 21can be allowed to deform along the weakened area. Thus, after theterminal board 21 and the fixing member 22 are engaged with each otherand mounted on the cap plate 10, when the cap plate 10 is deformed underthe thrust force of the gas inside the case, the terminal plate 21 andthe fixing member 22 can be deformed along with the cap plate 10.Therefore, it is possible to avoid that the terminal board 21 and thefixing member 22 cannot be deformed along with the deformation of thecap plate 10, which may cause the fixing member 22 and the cap plate 10to be disconnected from each other, eventually cause the terminal board21 to be detached from the cap plate 10 and raise the problem of airleakage or liquid leakage. As a result, the reliability of the secondarybattery can be further increased and the service life of the secondarybattery can be lengthened.

FIG. 11 is a schematic diagram of a three-dimensional structure of aterminal board 21 according to a third embodiment of the presentdisclosure. For ease of understanding, the same structures as in theterminal board 21 of the first embodiment are denoted by the samereference numerals, and the already described structures will not bedescribed again. As shown in FIG. 11, in other alternative embodiments,in order to enhance the deformability of the terminal board 21, it isalso possible to provide a weakened portion on the terminal board 21. Asan example, in the embodiment, the surface of the terminal board 21 onthe side close to the cap plate 10 may be provided with a notch 214along the radial direction. When the terminal board 21 is assembled tothe cap plate 10, the notch 214 extends in the length direction of thecap plate 10 and is located on the center line of the cap plate 10 inthe width direction thereof. In the embodiment, the notch 214 is engagedbetween two recesses 212 opposite to each other, but in otherembodiments, the notch 214 may be provided only on the surface of theterminal board 21 on the side close to the cap plate 10.

Thus, by providing the notch 214 to form the weakened portion of theterminal board 21 along the center line of the cap plate 10 in the widthdirection thereof, the terminal board 21 can be allowed to havedeformation along the weakened portion. After the terminal board 21 andthe fixing member 22 are engaged with each other and mounted on the capplate 10, the terminal board 21 and the fixing member 22 can be deformedalong with the cap plate 10 when the cap plate 10 is deformed by athrust force of the gas inside the case. Therefore, it is also possibleto further improve the reliability of the secondary battery and increasethe service life of the secondary battery.

In addition, in the above embodiments, in order to maintain theinsulation between the cap plate 10 and the electrode assembly insidethe case as well as between the cap plate 10 and a wiring board, thelower insulator 40 may be generally made of plastic material, have asubstantially plate shape, and be attached at the surface of the capplate 10 on the side facing the interior of the case. The lowerinsulator 40 may include two through holes and first insulators disposedaround the through holes. The two through holes are respectivelyopposite to the two electrode lead-out holes 11 provided on the capplate 10, while the first insulators are respectively disposed aroundthe periphery of the through holes.

Furthermore, in an alternative embodiment, an undercut 41 may beprovided on the surface of the lower insulator 40 facing the cap plate10. Correspondingly, an undercut hole to be matched with the undercut 41may be provided on the surface of the cap plate 10 facing the case. Withthe similar way of engagement between the undercut 225 and the undercuthole 13, the lower insulator 40 can be fixed to the cap plate 10 throughthe undercut 41 and the undercut hole on the cap plate 10, which willnot be described in detail here.

According to another embodiment of the present disclosure, there is alsoprovided a secondary battery including a case, an electrode assembly,and a cap assembly 100 in any of the above embodiments. The case has anopening. The electrode assembly is accommodated in the case and includesa first electrode plate, a second electrode plate, and a separatordisposed between the first electrode plate and the second electrodeplate. The cap assembly 100 covers the opening of the case to enclosethe electrode assembly in the case. Since the secondary battery has thesame advantages as the cap assembly 100 in the above embodiments, itwill not be described again.

In summary, in the secondary battery and the cap assembly of thesecondary battery according to embodiments of the present disclosure,the terminal board is fixed to the fixing member and the fixing memberis fixed to the cap plate through the connecting member, so that theterminal board is located on a side of the cap plate and covers theelectrode lead-out hole of the cap plate. Therefore, the electrodeterminal does not need to be provided with the base portion on thesurface of the cap plate on the side facing the interior of the batterycase. The space inside the case may not be occupied, thus the spaceoccupancy in the case of the secondary battery can be increased and theenergy density of the secondary battery can be further improved. Inaddition, by providing the weakened portion on the fixing member andclose to the center line of the cap plate in the width directionthereof, when the cap plate is deformed to form an arch due to the gasgenerated inside the case of the secondary battery, the fixing membercan be deformed along the weakened portion together with the cap plate.Thus it is possible to prevent an increase of gaps between both sides ofthe cap plate in the width direction and the fixing member and make thesealing member be always pressed tightly between the terminal board andthe cap plate. Therefore, the structural reliability of the cap assemblyof the secondary battery can be improved.

The invention may be embodied in other specific forms without departingfrom the spirit and essential characteristics thereof. The embodimentsdiscussed therefore should be considered in all aspects as illustrativeand not restrictive. The scope of the invention is defined by theappended claims rather than by the foregoing description, and thosemodifications falling within the meaning and equivalents of the claimsare thus intended to be embraced by the scope of the invention.Different technical features in different embodiments may be combined toobtain beneficial effects. Other variations of the described embodimentscan be understood and practiced by those skilled in the art uponstudying the drawings, the specification and the claims herein.

What is claimed is:
 1. A cap assembly for a secondary battery,comprising: a cap plate, a fixing member, and an electrode terminal,wherein: the cap plate has an electrode lead-out hole; the fixing memberis fixed to the cap plate and provided with a weakened portion that isclose to a center line of the cap plate extending in a length directionof the cap plate; and the electrode terminal comprises a terminal board,wherein the terminal board has an outer peripheral surface at leastpartially surrounded by the fixing member so that the electrode terminalis fixed to the fixing member, and the terminal board is provided on aside of the cap plate and covers the electrode lead-out hole, whereinthe terminal board is provided with two or more recesses spaced apartfrom each other in a circumferential direction on the outer peripheralsurface of the terminal board, the fixing member is provided with two ormore protrusions spaced apart from each other on an inner wall surfaceof the fixing member in contact with the terminal board, the protrusionsare matched with the recesses and are engaged with the recesses in asnap-fit manner to limit a relative rotation between the terminal boardand the fixing member, each recess is formed as a notch radially openedalong the outer peripheral surface of the terminal board and extendingthrough the entire terminal board in a thickness direction, and a partof the fixing member is clamped between a bottom surface of the terminalboard and the cap plate.
 2. The cap assembly of claim 1, wherein thefixing member comprises at least two weakened portions that arerespectively located on two sides of the electrode lead-out hole in alength direction of the cap plate as well as on the center line of thecap plate extending in the length direction of the cap plate.
 3. The capassembly of claim 1, wherein the weakened portion comprises an openingportion that is formed on a surface of the fixing member on a side awayfrom the cap plate.
 4. The cap assembly of claim 2, wherein the weakenedportion comprises an opening portion that is formed on a surface of thefixing member on a side away from the cap plate.
 5. The cap assembly ofclaim 3, wherein the opening portion penetrates through the fixingmember along a length direction of the cap plate; or the opening portionpenetrates through the fixing member along a thickness direction of thecap plate.
 6. The cap assembly of claim 4, wherein the opening portionpenetrates through the fixing member along a length direction of the capplate; or the opening portion penetrates through the fixing member alonga thickness direction of the cap plate.
 7. The cap assembly of claim 1,wherein the terminal board is provided with a notch on a surface of theterminal board on a side close to the cap plate or on a side away fromthe cap plate, and the notch extends along the length direction of thecap plate and is located at the center line of the cap plate extendingin the length direction of the cap plate.
 8. The cap assembly of claim1, further comprises an undercut and an undercut hole; the undercut holeis provided on a surface of the cap plate facing the fixing member; theundercut hole has an aperture gradually increasing along a directionfrom the fixing member to the cap plate; and the undercut is connectedto the fixing member and has a shape adapted to a shape of the undercuthole so as to be engaged with the undercut hole.
 9. The cap assembly ofclaim 2, further comprises an undercut and an undercut hole; theundercut hole is provided on a surface of the cap plate facing thefixing member; the undercut hole has an aperture gradually increasingalong a direction from the fixing member to the cap plate; and theundercut is connected to the fixing member and has a shape adapted to ashape of the undercut hole so as to be engaged with the undercut hole.10. The cap assembly of claim 5, further comprises an undercut and anundercut hole; the undercut hole is provided on a surface of the capplate facing the fixing member; the undercut hole has an aperturegradually increasing along a direction from the fixing member to the capplate; and the undercut is connected to the fixing member and has ashape adapted to a shape of the undercut hole so as to be engaged withthe undercut hole.
 11. The cap assembly of claim 6, further comprises anundercut and an undercut hole; the undercut hole is provided on asurface of the cap plate facing the fixing member; the undercut hole hasan aperture gradually increasing along a direction from the fixingmember to the cap plate; and the undercut is connected to the fixingmember and has a shape adapted to a shape of the undercut hole so as tobe engaged with the undercut hole.
 12. The cap assembly of claim 7,further comprises an undercut and an undercut hole; the undercut hole isprovided on a surface of the cap plate facing the fixing member; theundercut hole has an aperture gradually increasing along a directionfrom the fixing member to the cap plate; and the undercut is connectedto the fixing member and has a shape adapted to a shape of the undercuthole so as to be engaged with the undercut hole.
 13. The cap assembly ofclaim 1, further comprising a sealing member that is provided betweenthe terminal board and the cap plate and surrounds the electrodelead-out hole so as to seal the electrode lead-out hole.
 14. The capassembly of claim 13, wherein the sealing member is provided with anannular groove on a surface of the sealing member on a side facing thecap plate; the cap plate is provided with an annular flange to bematched with the groove on a surface of the cap plate on a side facingthe sealing member; and the flange is inserted into the groove.
 15. Asecondary battery, comprising: a case having an opening; an electrodeassembly accommodated in the case, comprising a first electrode plate, asecond electrode plate and a separator disposed between the firstelectrode plate and the second electrode plate; and the cap assembly ofclaim 1, wherein the cap assembly covers the opening of the case andencloses the electrode assembly in the case.
 16. The cap assembly ofclaim 1, wherein the fixing member comprises an accommodation space anda through hole penetrating the fixing member in a thickness direction ofthe cap plate, the accommodation space is an annular receiving grooveprovided on an inner wall surface of the through hole in acircumferential direction, and the terminal board is at least partiallyaccommodated in the accommodation space.
 17. The cap assembly of claim1, wherein two recesses of the two or more recesses are opposed to eachother and located on the center line of the cap plate extending in thelength direction of the cap plate.
 18. The cap assembly of claim 1,wherein the terminal board is formed as a circular sheet or plate.